Generally, the pelletization of plastics is frequently carried out by extruders in which the molten plastic starting material is pressed through the die orifices of a die plate into a cooling medium, such as water, wherein the material issuing from the die orifices of the die plate is cut off there by the blades of a rotating cutter head, this leading to the creation of pellets. Corresponding devices which execute, for example, processes for underwater pelletization are known as underwater pelletizers, such as SPHERO made by Automatik Plastics Machinery GmbH.
In such devices for pelletization, the high forces with which the blades of the cutter head are brought into contact with the die plate gives rise to a relatively high degree of wear on the die plate in the region of the die orifices, this resulting particularly in concentric wear marks on the die plate in the form of grooves. Starting from a certain depth of the grooves, it is necessary for the surfaces of die plates to be reground in order to ensure the reliable cutting-off of the issuing plastic material and so that there is no clumping or agglomeration of plastic material at the die orifices of the die plate, which might lead to a blockage of the die orifices of the die plate. Usually, die plates are removed from the pelletizer for regrinding, which means a considerable loss of time. Furthermore, it may be necessary at all times to have ready several sets of die plates that have, if necessary, already been reground, in order to minimize the time required for maintenance, during which time the pelletizer cannot be in operation.
Accordingly, a need exists for a device that can efficiently machine a die plate of an extruder without removing the die plate from the extruder. In addition, a further need exists for a device that can efficiently and accurately machine or re-machine a die plate of an extruder.
The present embodiments meet these needs.
The present embodiments are detailed below with reference to the listed Figures.